Data Layer Class Library Question

[bill_kearns]

I have a bunch of database methods that I normally copy and paste into my aspx code behind files on every web app I build.
That said, I was trying to build my next app by putting all of my connection info and data calls into a class library.
Then compile it as a DLL and reference it in my project. Does this make sense?
The thing I can't work out is in error handling. I usually put the exception message into a label with red font.
But in a library and a method is called which should return a Boolean value, How do I return the error message to the web form?

Here is a sample of what I have.
My aspx page would be requesting the result of validateDomainKey and supplying the string values.Thanks in advance.

using System;
using System.Data.SqlClient;
using System.Data;

namespace MyApp.Data
{
    public class Provider
    {
        private static String _sqlConnDev = @"Data Source=localhost;Initial Catalog=********;Persist Security Info=True;User ID=********;Password=********";
        public static String SqlConnDev
        {
            get
            {
                return _sqlConnDev;
            }
        }

        public bool validateDomainKey(String lic, String dom)
        {
            bool result = false;
            String connectionString = SqlConnDev;
            SqlConnection myConnection = new SqlConnection(connectionString);
            SqlCommand mySqlCommand = new SqlCommand("sp_validateLicense", myConnection);
            SqlDataReader MyReader = null;
            try
            {
                if (myConnection.State == ConnectionState.Closed)
                {
                    myConnection.Open();
                    mySqlCommand.CommandType = CommandType.StoredProcedure;
                    mySqlCommand.Parameters.AddWithValue("@license", lic);
                    mySqlCommand.Parameters.AddWithValue("@domain", dom);
                    MyReader = mySqlCommand.ExecuteReader();
                    if (MyReader.HasRows)
                    {
                        result = true;
                        MyReader.Close();
                    }
                }
            }
            catch (SqlException ex)
            {
                string ErrorMessage = "Could not connect to database: " + ex.Number + " " + ex.Message;
            }
            finally
            {
                if (mySqlCommand != null)
                {
                    mySqlCommand.Dispose();
                    mySqlCommand = null;
                }
                if (myConnection != null)
                {
                    if (myConnection.State == ConnectionState.Open)
                    {
                        myConnection.Close();
                    }
                }
            }
            return result;
        }
    }
}